Cardiovascular diseases like myocardial infarction, complex congenital heart disease, and subsequent heart failure are a leading cause of morbidity and mortality. Recent advances in tissue engineering arise to address the lack of available tissues and organs for transplantation because cells alone are not capable of recreating complex tissues upon transplantation. Consequently, a very promising approach to repair large scar areas and congenital heart defects may be the use of tissue engineering, in which cells are seeded in three-dimensional matrices of biodegradable polymers to form myocardial constructs. In recent years, there has been a tremendous increase in the understanding of stem cell biology. Stem cells have clonogenic and self-renewing capabilities, and under certain conditions, can differentiate into multiple cell lineages. Recent studies have shown that stem cells can be isolated from a wide variety of tissues, including bone marrow, peripheral blood, muscle, and adipose tissue. We hypothesize that tissue-engineered myocardial constructs with stem cells may fulfill the requirements of native heart muscle and, in the long run, may allow replacement of the injured heart and repair of congenital cardiac defects possible.